The grass genera of the world
Habit, vegetative morphology. Much-branched annual. Culms 10–40 cm high. Culm nodes glabrous. Culm internodes hollow. Leaves not basally aggregated; non-auriculate. Leaf blades linear; narrow; setaceous, or not setaceous; flat, or rolled (convolute); without cross venation; persistent. Ligule an unfringed membrane; truncate; 1.5–5 mm long.
Reproductive organization. Plants bisexual, all with bisexual spikelets; with hermaphrodite florets.
Inflorescence. Inflorescence paniculate; open (dichotomously-divaricately branched); with conspicuously divaricate branchlets; espatheate (but panicles partially enclosed by the upper leaf sheaths); not comprising partial inflorescences and foliar organs. Spikelet-bearing axes disarticulating, or persistent; falling entire, or disarticulating at the joints (disarticulation occurring variously at the bases of the spikelets, between them, or at bases of branches). Spikelets not secund; pedicellate.
Female-fertile spikelets. Spikelets 5–17 mm long; compressed laterally; disarticulating above the glumes, or falling with the glumes; not disarticulating between the florets (proximally), or disarticulating between the florets (distally). Rachilla prolonged beyond the uppermost female-fertile floret; the rachilla extension with incomplete florets. Hairy callus absent. Callus short.
Glumes two; relatively large; very unequal; shorter than the spikelets; shorter than the adjacent lemmas; pointed, or not pointed; shortly awned, or awnless; carinate; similar (membranous). Lower glume 1–3 nerved. Upper glume 1–5 nerved. Spikelets with incomplete florets. The incomplete florets distal to the female-fertile florets.
Female-fertile florets 2–12. Lemmas similar in texture to the glumes (with hyaline margins); not becoming indurated; incised; usually 2 lobed (emarginate or bifid); awnless, or mucronate, or awned. Awns when present, 1; from a sinus, or dorsal; from near the top; much shorter than the body of the lemma; entered by one vein. Lemmas hairless; non-carinate (3-keeled); 3–5 nerved. Palea present; relatively long; entire (acute to truncate), or apically notched (bifid); awnless, without apical setae; 2-nerved; 2-keeled. Lodicules present; 2; free; membranous; ciliate; toothed. Stamens 3. Anthers 0.5–1.3 mm long; not penicillate. Ovary apically glabrous. Styles free to their bases. Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; longitudinally grooved; trigonous. Hilum short (elongated, but short). Embryo small. Endosperm liquid in the mature fruit, or hard; without lipid. Embryo with an epiblast; without a scutellar tail; with a negligible mesocotyl internode. Embryonic leaf margins meeting.
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae absent. Long-cells of similar wall thickness costally and intercostally (very large). Mid-intercostal long-cells fusiform; having straight or only gently undulating walls. Microhairs absent. Stomata common. Subsidiaries parallel-sided. Guard-cells overlapped by the interstomatals. Intercostal short-cells absent or very rare. Costal short-cells neither distinctly grouped into long rows nor predominantly paired. Costal silica bodies horizontally-elongated crenate/sinuous to horizontally-elongated smooth, or panicoid-type; often dumb-bell shaped.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma. Leaf blade with distinct, prominent adaxial ribs, or nodular in section; with the ribs more or less constant in size. Midrib with one bundle only. Bulliforms not present in discrete, regular adaxial groups (at least, bulliforms/groups inconspicuous in the poor material seen). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders absent. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 7. 2n = 14. 2 ploid. Chromosomes large.
Classification. Watson & Dallwitz (1994): Pooideae; Poodae; Poeae. Soreng et al. (2015): Pooideae; Poodae; Poeae; Parapholiinae. 6 species.
Distribution, phytogeography, ecology. Mediterranean, western Asia.
Xerophytic; species of open habitats; halophytic, or glycophytic. Mostly in maritime sands or coastal rocky hills.
Economic aspects. Important native pasture species: C. memphitica.
Rusts and smuts. Rusts Puccinia. Taxonomically wide-ranging species: Puccinia hordei. Smuts from Ustilaginaceae. Ustilaginaceae Ustilago.
References, etc. Morphological/taxonomic: Stace 1978b. Leaf anatomical: this project.
Illustrations. • C. dichotoma: Fl. Iraq, 1968. • Inflorescence detail
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 13th November 2017. delta-intkey.com/grass’.